Automated fuel dispensing systems and semi-automated fuel dispensing systems have been devised to permit unattended or semi-unattended purchases of fuel by authorized customers of such systems. Customers using systems of this type typically include municipalities, large trucking companies, and the like. When only a single customer uses a given facility, control of the fuel dispensing facility is relatively simple. When the system, however, is required to serve many different customers or a single customer with a large number of drivers and vehicles, it generally is necessary to have an attendant on duty at a central location in the station for billing purposes. Typically systems of this latter type are the commonly known "self-service" gasoline stations which have a central location manned by an attendant who monitors volume readers and the pump turn-on switch controls for the fuel pumps located at the station. The customers pump their own fuel and then go to the central location to pay for the fuel or otherwise take care of the billing.
Fully automatic self-service fuel dispensing systems have been developed in which a credit card or specially prepared document is inserted into a card reader to cause selected data from the card to be transmitted to a remote central computer for verification. If the document is verified as an authorized document, the system then permits the withdrawal of fuel under the control of the credit card. The quantity of the fuel withdrawn is monitored; and upon completion of the transaction, data representative of this quantity is transmitted by the local controller along with the credit card identification to the central computer for processing on the particular account number indicated by the credit card being used. While such a system permits the completely unattended operation of a fuel dispensing service station for customers having credit cards usable in the system, it requires committed transmission links between the location of the fuel pumps and the central computer location.
An improvement is fully automatic self-service fuel dispensing systems which localizes the credit card identification and verification check of such credit cards is disclosed in the above mentioned related patent. That system includes logic circuitry at a local control console associated with the card reader for identifying and verifying the credit card as well as controlling and recording the data relative to the transaction itself. A store and forward memory then is utilized to temporarily store the information relative to each transaction until that information is to be forwarded to a central computer for further processing.
In systems of the type disclosed in the above identified related patent, variations include the use of a local computer or microprocessor at a central location within the fuel dispensing station itself. For example, a number of card readers each can be located in a different fuel pump island within the terminal for individually controlling a group of fuel dispensing pumps or the like. Typically a single card reader is used to control four or more pumps at an individual island. A number of such islands, all linked with the central computer at the station, are used in a large automatic bulk fueling station.
Operation of the system relays which actually control the ultimate dispensing of fuel from the various fuel pumps and the like is effected through decoding of the data at the card readers by the central computer. The central computer then supplies serial polling signals in some pre-established sequence over a polling signal line to the different control terminals at each of the islands. At the islands, the polling signals are decoded to uniquely operate the relays at the island in accordance with the signals supplied to it. Generally such systems include an automatic turn-off or shut down of the relays in the event of power failure or the like. Situations exist, however, where a failure of the computer may occur without a power failure at the station. In such an event, it is desirable to render the system relays at each of the islands inoperative to prevent spillage of fuel or unauthorized withdrawal of fuel whenever such a failure occurs. In addition it is desirable to continuously monitor the status of operation of all of the relays at the various island consoles or sub-terminals at the central computer to insure that the operation as it actually exists is in accordance with the polling signals supplied from the computer to the various terminals to initiate the operation.